Changes in CT morphology can be an independent response marker for patients receiving regorafenib for colorectal liver metastases: retrospective pilot study

BACKGROUND: Regorafenib is a multi-kinase inhibitor, which was shown to be effective for patients with metastatic colorectal cancer refractory to standard therapies. However, its patterns of response has not yet been fully understood. METHODS: Clinical records of 10 patients who received regorafenib for evaluable colorectal liver metastases were reviewed. Response to chemotherapy was evaluated with the RECIST and morphologic response criteria, and its clinical relevance was analyzed. RESULTS: All patients received multiple lines of fluorouracil-based chemotherapy before regorafenib. The median follow-up duration after introduction of regorafenib was 4.9 months (range, 2 to 12.5 months). Median number of chemotherapy cycles was 2 (range, 1 to 15). In size-based response evaluation, 4 patients presented SD and 6 patients showed PD according to the RECIST. In non-size-based response evaluation, 3 patients were classified as optimal morphologic response and 7 patients were categorized as suboptimal morphologic response. Patients who presented optimal morphologic response showed significantly longer progression-free survival compared with those presented suboptimal response (median, 4.9 months vs. 0.7 months; P = 0.028), while size-based response evaluation could not well stratify patient prognosis. CONCLUSION: Non-size-based CT morphologic response could be a potential alternative response marker for patients treated with regorafenib. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12885-018-4067-5) contains supplementary material, which is available to authorized users.